Design Of Amplitude Adaptive Emergency DC Power Support For LCC HVDC Transmission

With the introduction of DC lines in the power system, the network characteristics are becoming more and more complex. From single DC line interconnection to parallel operation of DC and AC lines and multi-infeed DC systems, the influence of DC lines on entire power network operation is becoming more and more prominent. Complex network structure will pose greater problems to network in terms of security, stability and control. But at the same time the quick control and rapid response of DC lines have brought a huge research attention in the area of Emergency Control of DC lines.Multi circuit HVDC systems provides a higher power support capacity and flexibility and are capable of mutual support, therefore significantly enhancing the stability of entire power network. Therefore, the study on efficient emergency control strategy for multi in feed HVDC system will not only result in the better utilization of HVDC resources but also im-prove the stability of the entire AC network.The power on the bipolar HVDC links can be increased or decreased by varying the current order of the HVDC converters. In event of fault in the neighboring AC network, the power fluctuations can. be absorbed by the HVDC lines keeping in mind their overload capa-bility; based on Extended Equal Area Criterion (EEAC). This control strategy is technically termed as Emergency DC Power Support (EDCPS).This dissertation gives an introduction to a commonly used Emergency DC Power Sup-port (EDCPS) technique, which ramps up the power on the High Voltage Direct Current transmission lines during emergency situation & than presents an improved technique, here-after named as Amplitude adaptive EDCPS (AAEDCPS) for increasing the power on HVDC line quickly and with the consideration of maximum power carrying capability of HVDC line as well as converter station equipment; while keeping in account the AC-DC system stability. The later technique increases the power stepwise on the basis of feedback from the system takes a decision whether to increase the power further or not. The network of Eastern China Power System, Central China Power System and three parallel HVDC lines with a power carrying capability of 7200MW, connecting the two networks have been modeled and simu-lated in PSCAD for the purpose of making this study. The algorithm for AAEDCPS has been implemented in PSCAD/EMTDC in the form of custom designed block and Fortran77 script. PSCAD/EMTDC simulation model has been used as an inner objective function calculation loop for a non-linear optimization algorithm i.e. Golden Intersection; for finding the optimal AAEDCPS control parameters. Analysis and comparison of the simulation results of Ramp type EDCPS, AAEDCPS (with and without optimal parameter) has been discussed and pre-sented in this dissertation. Some recommendations about future work in the area of Emer-gency control have been made as well.